Bài giảng Introduction to Software Engineering - Week 1: Overview - Nguyễn Thị Minh Tuyền

Introduction to Software Engineering
 Week 1: Overview
 Objectives 
£ understand what software engineering is and why
 it is important;
£ understand that the development of different types
 of software system may require different software
 engineering techniques;
£ understand ethical and professional issues that are
 important for software engineers;
 2
 Topics covered
1. Software
2. Software engineering
3. Software process
4. Software engineering ethics
 3
 Topics covered
1. Software
2. Software engineering
3. Software process
4. Software engineering ethics
 4
 What is software?
£ Computer programs and associated
 documentation.
£ Software products
 p may be developed for a particular customer or
 p may be developed for a general market.
 5
 Role of software [1]
q Is software important? Why?
q Give ten examples of software
 6
 Role of software [2]
£ The economies of ALL developed nations are
 dependent on software.
£ More and more systems are software controlled
£ Software engineering is concerned with theories,
 methods and tools for professional software
 development.
 7
 Software products
£ Generic products
 p Stand-alone systems that are marketed and sold to
 any customer who wishes to buy them.
 p The specification of what the software should do is
 owned by the software developer and decisions on
 software change are made by the developer.
£ Customized products
 p Software that is commissioned by a specific customer
 to meet their own needs.
 p The specification of what the software should do is
 owned by the customer for the software and they make
 decisions on software changes that are required.
 8
 Essential attributes of good software
£ Maintainability
 p Software should evolve to meet the changing needs of
 customers.
£ Dependability and security
 p Software dependability includes a range of characteristics
 including reliability, security and safety.
£ Efficiency
 p Software should not make wasteful use of system resources.
£ Acceptability
 p Software must be acceptable to the type of users for which it is
 designed.
 9
 Topics covered
1. Software
2. Software engineering
3. Software process
4. Software engineering ethics
 10
Building real things ...
 How about producing a software?
 11
 FAQs about Software Engineering
1. What is software engineering?
2. What are the fundamental software engineering activities?
3. What is the difference between software engineering and
 computer science?
4. What is the difference between software engineering and
 system engineering?
5. What are the key challenges facing software engineering?
6. What are the costs of software engineering?
7. What are the best software engineering techniques and
 methods?
8. What is software process?
 12
 History of software engineering
£ Software crisis
£ The term 'software engineering' was suggested at
 conferences organized by NATO in 1968 to
 discuss the 'software crisis'.
£ The adoption of an engineering approach to
 software development would
 p reduce the costs of software development
 p lead to more reliable software.
 13
 What is software engineering?
£ Software engineering is an engineering discipline that is
 concerned with all aspects of software production from the
 early stages of system specification through to maintaining
 the system after it has gone into use.
£ Engineering discipline
 p Using appropriate theories and methods to solve
 problems bearing in mind organizational and financial
 constraints.
£ All aspects of software production
 p Not just technical process of development. Also project
 management and the development of tools, methods
 etc. to support software production.
 14
Layered Technology
 tools
 methods
 process model
 a quality focus
 Software Engineering
 15
 Software costs
£ Software costs often dominate computer system
 costs. The costs of software on a PC are often
 greater than the hardware cost.
£ Software costs more to maintain than it does to
 develop. For systems with a long life, maintenance
 costs may be several times development costs.
£ Software engineering is concerned with cost-
 effective software development.
 16
 Costs of software engineering
£ Roughly 60% of software costs are development
 costs, 40% are testing costs.
£ For custom software, evolution costs often exceed
 development costs.
 17
Software costs
 18
 Software engineering vs. Computer 
 science?
£ Computer science focuses on theory and
 fundamentals.
£ Software engineering is concerned with the
 practicalities of developing and delivering useful
 software.
 CS SE
 19
 Software engineering vs. System 
 engineering?
£ System engineering is concerned with all aspects
 of computer-based systems development including
 hardware, software and process engineering.
£ Software engineering is part of this more general
 process.
 System engineering Software engineering
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 Best software engineering techniques and 
 methods?
£ While all software projects have to be
 professionally managed and developed, different
 techniques are appropriate for different types of
 system.
£ You can’t say that one method is better than
 another.
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Software failure: The Ariane launcher 
 accident
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 Importance of software engineering
£ More and more, individuals and society rely on
 advanced software systems. We need to be able
 to produce reliable and trustworthy systems
 economically and quickly.
£ It is usually cheaper, in the long run, to use
 software engineering methods and techniques for
 software systems rather than just write the
 programs as if it was a personal programming
 project.
 p For most types of system, the majority of costs are the
 costs of changing the software after it has gone into use.
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 Topics covered
1. Software
2. Software engineering
3. Software process
4. Software engineering ethics
 24
 What is software process?
£ A sequence of activities that leads to the
 production of a software product.
£ There are four fundamental activities that are
 common to all software processes.
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 Software process activities
£ Software specification
 p customers and engineers define the software that is to
 be produced and the constraints on its operation.
£ Software development
 p software is designed and programmed.
£ Software validation
 p software is checked to ensure that it is what the
 customer requires.
£ Software evolution
 p software is modified to reflect changing customer and
 market requirements.
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 General issues that affect software [1]
£ Heterogeneity
 p Increasingly, systems are required to operate as
 distributed systems across networks that include
 different types of computer and mobile devices.
£ Business and social change
 p Business and society are changing incredibly quickly as
 emerging economies develop and new technologies
 become available. They need to be able to change their
 existing software and to rapidly develop new software.
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 General issues that affect software [2]
£ Security and trust
 p As software is intertwined with all aspects of our lives, it
 is essential that we can trust that software.
£ Scale
 p Software has to be developed across a very wide range
 of scales, from very small embedded systems in
 portable or wearable devices through to Internet-scale,
 cloud-based systems that serve a global community.
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 Software engineering diversity
£ There are many different types of software system
 and there is no universal set of software
 techniques that is applicable to all of these.
£ The software engineering methods and tools used
 depend on
 p the type of application being developed,
 p the requirements of the customer and
 p the background of the development team.
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 Application types
£ Stand-alone applications
 p These are application systems that run on a local computer, such
 as a PC. They include all necessary functionality and do not need
 to be connected to a network.
£ Interactive transaction-based applications
 p Applications that execute on a remote computer and are
 accessed by users from their own PCs or terminals. These
 include web applications such as e-commerce applications.
£ Embedded control systems
 p These are software control systems that control and manage
 hardware devices. Numerically, there are probably more
 embedded systems than any other type of system.
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 Application types
£ Batch processing systems
 p These are business systems that are designed to process data in
 large batches. They process large numbers of individual inputs to
 create corresponding outputs.
£ Entertainment systems
 p These are systems that are primarily for personal use and which are
 intended to entertain the user.
£ Systems for modeling and simulation
 p These are systems that are developed by scientists and engineers
 to model physical processes or situations, which include many,
 separate, interacting objects.
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 Application types
£ Data collection systems
 p These are systems that collect data from their environment using a
 set of sensors and send that data to other systems for processing.
£ Systems of systems
 p These are systems that are composed of a number of other
 software systems.
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 Software engineering fundamentals
£ Some fundamental principles apply to all types of
 software system, irrespective of the development
 techniques used:
 p Systems should be developed using a managed and
 understood development process. Of course, different
 processes are used for different types of software.
 p Dependability and performance are important for all types of
 system.
 p Understanding and managing the software specification and
 requirements are important.
 p Where appropriate, you should reuse software that has
 already been developed rather than write new software.
 33
 Internet software engineering
£ The Web is now a platform for running application
 and organizations are increasingly developing
 web-based systems rather than local systems.
£ Web services allow application functionality to be
 accessed over the web.
£ Cloud computing is an approach to the provision of
 computer services where applications run remotely
 on the ‘cloud’.
 p Users do not buy software buy pay according to use.
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 Web-based software engineering
£ Web-based systems are complex distributed
 systems but the fundamental principles of software
 engineering discussed previously are as applicable
 to them as they are to any other types of system.
£ The fundamental ideas of software engineering
 apply to web-based software in the same way that
 they apply to other types of software system.
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 Web software engineering
£ Software reuse
£ Incremental and agile development
£ Service-oriented systems
£ Rich interfaces
 36
 Topics covered
1. Software
2. Software engineering
3. Software process
4. Software engineering ethics
 37
 Software engineering ethics
£ Software engineering involves wider responsibilities than
 simply the application of technical skills.
£ Software engineers must behave in an honest and ethically
 responsible way if they are to be respected as
 professionals.
£ Ethical behaviour is more than simply upholding the law but
 involves following a set of principles that are morally
 correct.
 38
 Issues of professional responsibility
£ Confidentiality
 p Engineers should normally respect the confidentiality of their
 employers or clients irrespective of whether or not a formal
 confidentiality agreement has been signed.
£ Competence
 p Engineers should not misrepresent their level of competence. They
 should not knowingly accept work which is outwith their
 competence.
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 Issues of professional responsibility
£ Intellectual property rights
 p Engineers should be aware of local laws governing the use of
 intellectual property such as patents, copyright, etc. They should be
 careful to ensure that the intellectual property of employers and
 clients is protected.
£ Computer misuse
 p Software engineers should not use their technical skills to misuse
 other people’s computers. Computer misuse ranges from relatively
 trivial (game playing on an employer’s machine, say) to extremely
 serious (dissemination of viruses).
 40
 ACM/IEEE Code of Ethics
£ The professional societies in the US have cooperated to
 produce a code of ethical practice.
£ Members of these organisations sign up to the code of
 practice when they join.
£ The Code contains eight Principles related to the behaviour
 of and decisions made by professional software engineers,
 including practitioners, educators, managers, supervisors
 and policy makers, as well as trainees and students of the
 profession.
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 The ACM/IEEE Code of Ethics: 
 PREAMBLE 
£ The short version of the code summarizes aspirations at a high level of
 the abstraction; the clauses that are included in the full version give
 examples and details of how these aspirations change the way we act
 as software engineering professionals. Without the aspirations, the
 details can become legalistic and tedious; without the details, the
 aspirations can become high sounding but empty; together, the
 aspirations and the details form a cohesive code.
£ Software engineers shall commit themselves to making the analysis,
 specification, design, development, testing and maintenance of
 software a beneficial and respected profession. In accordance with
 their commitment to the health, safety and welfare of the public,
 software engineers shall adhere to the following Eight Principles:
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 Ethical principles
1. PUBLIC - Software engineers shall act consistently with the public interest.
2. CLIENT AND EMPLOYER - Software engineers shall act in a manner that is in the best
interests of their client and employer consistent with the public interest.
3. PRODUCT - Software engineers shall ensure that their products and related
modifications meet the highest professional standards possible.
4. JUDGMENT - Software engineers shall maintain integrity and independence in their
professional judgment.
5. MANAGEMENT - Software engineering managers and leaders shall subscribe to and
promote an ethical approach to the management of software development and
maintenance.
6. PROFESSION - Software engineers shall advance the integrity and reputation of the
profession consistent with the public interest.
7. COLLEAGUES - Software engineers shall be fair to and supportive of their colleagues.
8. SELF - Software engineers shall participate in lifelong learning regarding the practice of
their profession and shall promote an ethical approach to the practice of the profession.
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